The present invention is directed to a multi-functional electrographic printer device for single-sided or both-sided printing of web-shaped recording media in start/stop mode.
A high economic benefit to the customer and a broad spectrum of flexibility are expected from modern electrographic printer systems to a greatly increasing extent. Both the effective utilization of printing materials as well as the flexible fashioning of the print information play a large part therein.
Endlessly processing (fan-fold) electrographic printer systems that print a web-shaped recording medium on one side have prevailed everywhere in the marketplace where a high device availability given high printing volume and a broad spectrum of material to be printed are demanded. These printer systems, however, have the disadvantage that it is not possible to change between single-sided and double-sided printing. For the user, this leads both to an economically unfavorable situation as well as being contrary to contemporary demands to maximize raw materials"" utilization. Many customized applications wherein double-sided printing is compulsory (brochures, books, etc.) can thus not be satisfied, especially since electrographic high-performance printers are especially efficient when they are operated as free of interruption as possible.
For producing multi-color and double-sided printing with electrographic printer devices processing continuous stock, European Patent Document EP-B1-01 54 695 discloses that two continuous stock printers be operated following one another, whereby the paper printed in the first printer is turned over and is subsequently printed on the second side in the second printer.
The outlay for this known system is substantial due to the required, second printer.
The reference publication IBM Technical Disclosure Bulletin, Vol.22, No.6, November 1979, page 2466, in FIG. 2, also discloses an electrophotographic printer device for printing web-shaped recording media with which it is possible to print on both sides of the recording medium. To this end, the recording medium is pulled from a supply stack, supplied to a transfer printing station and provided with toner images on one side. After the toner fixing step, the recording medium is turned over and is resupplied to the transfer printing station. Another fixing in the fixing station ensues after the back side of the recording medium has been printed with toner images.
This old reference fundamentally discloses duplex printing with continuous stock recording media. The proposal, however, never led to a product. Further, the electrographic printer device disclosed therein is only suited for both-sided printing of the recording medium. A change of operating modes is not provided.
The reference publication Xerox Disclosure Journal, Vol.9, No.3, May 1984, Stanford, Conn., USA, pages 201 through 203, xe2x80x9cMethod for Duplex Printing on Continuous Web Paperxe2x80x9d, fundamentally discloses the possibility of printing continuous stock in simplex printing and duplex printing with one printer.
The known apparatus, however, does not include a switchable defection means, and an adaptation of the fixing station is required when changing operating modes.
The high-precision allocation of the individual device components needed for the operation of the printer device continues to require a stable structure of the apparatus.
High-performance printer devices for continuous stock paper are increasingly developing into components of extensive systems wherein the pre-processing and after-processing of the papers, backside and color printing play an increasing role in addition to the actual print production. A structure that enables a flexible adaptation to the system environment is therefore advantageous.
An object of the present invention is to provide an electrographic printer device for printing web-shaped recording media in changing operating modes with one and the same apparatus that is flexible constructed and that enables an adaptation to the greatest variety of user demands by the user in a simple way.
This and other objects and advantages of the invention are achieved by a multi-functional electrographic printer device for printing web-shaped recording media, having a motor-driven intermediate carrier with a means that generates toner images on the intermediate carrier; a first transfer printing station with controllable transfer printing means via which the toner images are transferred onto the recording medium in a transfer printing status and the toner images are left on the intermediate carrier in a rejection status; a second transfer printing station following the first transfer printing station in the conveying direction of the intermediate carrier, with controllable transfer printing means in order to transfer the toner images onto the recording medium in a transfer printing status; a recording medium transport channel arranged between the first and the second transfer printing station, having one or more added buffer storages dependent on the printer mode, as well as a turn-over means for the recording medium; and a fixing station following the second transfer printing station in the conveying direction.
Advantageous embodiments of the invention include an intermediate fixing station that at least partially fixes the toner images transferred onto the recording medium by the first transfer printing station, and in particular, have the intermediate fixing station and/or the fixing station fashioned as a photoflash fixing means.
The printer device may include a simplex transport channel that directly supplies the recording medium to the second transfer printing station proceeding from a supply region. It is also contemplated to include a means that produces toner images with preselectable color on the intermediate carrier. Preferably, a buffer storage that precedes the fixing station in recording medium conveying direction is provided. The buffer storage may be a looper.
In exemplary embodiments, a means for pivoting a transfer printing station in against and away from the intermediate carrier is provided.
The present invention also provides a method for two-sided printing of web-shaped recording media with a multi-functional electrographic printer device, including: generating a first sequence of toner images allocated to the front side of the recording medium and a second sequence of toner images allocated to the back side of the recording medium on a motor-driven intermediate carrier; transferring the first sequence of toner images onto the front side of the recording medium via a first transfer printing station and mechanical intermediate storage and turn-over of the recording medium printed with said first sequence; transferring the second sequence of toner images onto the back side of the recording medium via a second transfer printing station following the first transfer printing station in conveying direction of the intermediate carrier with the first transfer printing station deactivated; and fixing the toner images on the recording medium via a fixing station that follows the second transfer printing station in the conveying direction.
The method may provide that the toner images are intermediately fixed on the recording medium after the transfer of the first sequence of toner images.
In the inventive printer device, two transfer printing stations are arranged at the circumference of the photoconductive drum, whereby the first transfer printing station serves for printing the front side and the second serves for printing the back side. A mechanical intermediate storage area for the recording medium as well as a turn-over station are located between the transfer printing stations. For two-sided printing of the recording medium, the front side is printed first with the first transfer printing station, whereby the second transfer printing station is swivelled out and the paper does not move there. The paper runs from the first transfer printing station into the mechanical storage area and is subsequently turned over in a turn-over station. After the transfer printing operation of the front side, the paper transport to the first transfer printing station is stopped, this station is swivelled out, and the back side is then printed with the assistance of the second transfer printing station. The paper thereby runs from the intermediate storage area. Subsequently, the loose toner images are fixed in a thermal fixing station.
This alternating front/back printing with sheet-by-sheet start/stop of the paper web roughly corresponds to the printing rhythm of a single sheet machine with a duplex mode.
In order to prevent potential damage to the toner image of the front side during turning, an intermediate fixing with the assistance of a photoflash fixing means preceding the turn-over station can be advantageous.
The total of the printing times for both sides of the paper is available for conducting the final fixing step in the thermal fixing station; as a result thereof, fixing can be implemented interruption-free and at half speed. This enables a high fixing quality.
The start/stop mode can be suppressed for longer simplex printing and the paper is continuously printed with the first transfer printing station, for example with the second transfer printing station swivelled out, or a transfer printing ensues only via the second transfer printing station given direct feed via a separate simplex channel.
The printer means also makes it advantageously possible to printed a page with two-color printing, for example in what is referred to as the spot color method. To that end, a first, single-color toner image is generated via the first transfer printing station and a superimposed second image is then produced with the second transfer printing station.
It is likewise possible to print the front side with one color and to print the back side with a second color.
Overall, the tolerance variations of the print image registration precision is caused by only one device, this doubling the precision compared to the use of two coupled printers for generating duplex printing.